As computer networks have grown larger and more complex, a variety of operating protocols have evolved. Often, it is desirable to allow communication between widely spaced networks of a given protocol that are not directly connected for that protocol. Various methods have been developed to facilitate this function. Two main problems impair communication between these "foreign" protocols (i.e. protocols that are different from the most frequently used protocol in the network).
First, in hierarchical networks, it is difficult to find out information about destinations located in other network areas. In particular, it is extremely difficult to find destinations in other network areas that support a foreign protocol. Prior attempts to allow communication between foreign protocol destinations have contemplated the passage of information about the location of foreign protocol destinations from a router in which the foreign protocol destination is contained to one other area. In other words, routers in previously known systems have the capability of passing address information about foreign protocol destinations to one other area. No facility exists that allows a level two router receiving the foreign protocol destination information to pass it to other network areas.
Second, assuming that the locations of foreign protocol destinations are known, the efficient transfer of foreign protocol information between network areas has been hindered by logistical difficulties encountered merely by attempting to traverse network areas that operate under a different protocol. One specific problem is that presently existing methods of passing foreign protocol information do not efficiently account for basic differences between the way the cost of the transfer is calculated by the differing protocols. Another shortcoming of prior art systems is that they do not provide any means to optimize the routing of foreign protocol information between areas. A method of transferring foreign protocol information across a hierarchical backbone network that overcomes the aforementioned problems is desirable.